1. Field of the Invention
This invention relates to a write head for a fluorescent printer which is effectively used as a write head for an optical printer.
2. Discussion of Background
In general, an optical printer is so constructed that a recording medium such as a photosensitive drum charged is irradiated on a surface thereof with light in a dot-like manner to form a latent image of a letter, a figure or the like on the recording medium, which latent image is then developed and transferred onto a recording paper. As a write head for such an optical printer is conventionally known a write head for a fluorescent printer which utilizes a principle of a fluorescent display device, which is typically exemplified in, for example, Japanese Patent Application Laid-Open Publication No. 200443/1985.
In an optical write device disclosed in the Japanese publication, a plurality of dot-like anodes each comprising an anode conductor and a phosphor layer deposited thereon are provided on a substrate. Groups of dot-like anodes are arranged in a manner to be spaced from each other at a predetermined interval in a main scanning direction (which is a direction of rotation of a photosensitive drum), resulting in forming anode arrays. The anode arrays are juxtaposed in two rows in a sub-scanning direction (which is a direction of movement of the photosensitive drum or a direction perpendicular to the main scanning direction). The anodes of each of the anode arrays are arranged in a manner to be positioned at different positions or deviated from each other in the main scanning direction. More particularly, the anodes of each anode array which are adjacent to each other are arranged in a zigzag manner and each pair of the anodes are integrally connected to each other through a wiring conductor which is formed into the same width as each anode conductor.
The conventional optical write device also includes insulating layers arranged in three rays in the main scanning direction, which are formed by depositing insulating paste on an outer side of each of the anode arrays and between both anode arrays by thick film printing techniques. The insulating layers are provided thereon with control electrodes for the respective anode arrays. The control electrodes each are made of a mesh-like metal material. Also, the conventional optical write device includes filamentary cathodes arranged above the control electrodes.
Unfortunately, the conventional optical write device constructed as described above has some disadvantages.
In the optical write device, the insulating layers underlie the control electrodes, so that they each are charged on a surface thereof with electrons to form a negative electric field in proximity to the anodes, resulting in display defects occurring.
Another disadvantage of the conventional optical write device is that it fails to form a pattern of the insulating layers with high accuracy because they are formed into a large thickness, therefore, it is substantially impossible to provide the insulating layer in a space between the anode arrays which has a width as small as 1 mm or less.
A further disadvantage of the conventional optical write device is that it is highly difficult to provide two mesh-like control electrodes on a surface of the insulating layer between the anode arrays while keeping the control electrodes electrically non-conductive.
Actually, the above-described disadvantages of the conventional optical write device prevent it from being put to practical use.
Accordingly, it is an object of the present invention to provide a write head for a fluorescent printer which is capable of effectively prevented from being adversely affected by charging of electrons and an electric field generated by opposite control electrodes.